Antenna port compatibility signaling

ABSTRACT

Methods, systems, and devices for wireless communication are described. A user equipment (UE) capable of supporting multiple antenna ports may determine that some combinations of antenna ports can be used simultaneously. The UE may make this determination by evaluating the relationships between the physical antennas and the transmit chains included in the UE. Upon determining that the combinations of antenna ports can be used simultaneously, the UE may send a message to a base station. The message may indicate whether two or more antenna ports can be used at the same time. The UE may communicate simultaneously over one or more antenna ports based on the scheduling information from the base station which takes into account the ability of the combination of antenna ports to be used concurrently.

CROSS-REFERENCES

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 16/007,771 by Sundararajan et al., entitled“Antenna Port Compatibility Signaling” and filed Jun. 13, 2018, whichclaims priority to Greek Provisional Patent Application No. 20170100272by Sundararajan et al., entitled “Antenna Port Compatibility Signaling”and filed Jun. 16, 2017, each of which is assigned to the assigneehereof and expressly incorporated by reference in its entirety.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to antenna port compatibility signaling.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system, or a New Radio (NR) system). A wireless multiple-accesscommunications system may include a number of base stations or accessnetwork nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

In some cases, a UE may include multiple antenna ports that the UE canuse simultaneously to increase communication performance. However, notall combinations of the UE's antenna ports may support simultaneoustransmission or reception. For example, a pair of antenna ports may beconfigured so that simultaneous transmission or reception is notpossible. Scheduling of uplink or downlink transmissions by a basestation for unsupported combinations of antenna ports may impairreception of the downlink or uplink transmissions.

SUMMARY

The described techniques relate to improved methods, systems, devices,or apparatuses that support antenna port compatibility signaling. A userequipment (UE) with multiple antenna ports may determine which of theantenna ports can be used concurrently and which cannot. For example,the UE may determine that a first combination of antenna ports can beused concurrently but that another combination of antenna ports cannotbe used concurrently. The antenna ports that cannot be used concurrentlymay be constrained by the number of transmit chains available or by theconnection of the transmit chains to the physical antennas associatedwith the antenna ports. After determining the combinations of antennaports that can and cannot be used concurrently, the UE may convey thisinformation to a base station responsible for scheduling the UE. In somecases, the UE may report a delay constraint for the combinations ofantenna ports that cannot be used concurrently. This delay constraintmay indicate how long the UE must wait in between using differentantenna ports in a combination that does not support concurrent use. Thebase station may leverage the information from the UE to schedulecommunications with the UE. For example, the base station may schedulethe UE in a manner that takes advantage of the antenna ports that can beused concurrently. The base station may avoid scheduling communicationswith the UE that require concurrent use of antenna ports that have beenreported as incompatible for concurrent use.

A method of wireless communication at a user equipment (UE) having aplurality of antenna ports is described. The method may includeidentifying a compatibility of at least one antenna port combination ofthe plurality of antenna ports for coincident use by the UE,transmitting a message to a base station indicating whether two or moreantenna ports are available for coincident use based at least in part onthe identified compatibility, and communicating with the base stationvia at least one of the plurality of antenna ports. The at least one ofthe plurality of antenna ports may be selected based at least in part onthe identified compatibility.

An apparatus for wireless communication at a user equipment (UE) havinga plurality of antenna ports is described. The apparatus may includemeans for identifying a compatibility of at least one antenna portcombination of the plurality of antenna ports for coincident use by theUE, means for transmitting a message to a base station indicatingwhether two or more antenna ports are available for coincident use basedat least in part on the identified compatibility, and means forcommunicating with the base station via at least one of the plurality ofantenna ports. The at least one of the plurality of antenna ports may beselected based at least in part on the identified compatibility.

Another apparatus for wireless communication at a user equipment (UE)having a plurality of antenna ports is described. The apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to identify a compatibility of atleast one antenna port combination of the plurality of antenna ports forcoincident use by the UE, transmit a message to a base stationindicating whether two or more antenna ports are available forcoincident use based at least in part on the identified compatibility,and communicate with the base station via at least one of the pluralityof antenna ports. The at least one of the plurality of antenna ports maybe selected based at least in part on the identified compatibility.

A non-transitory computer readable medium for wireless communication ata user equipment (UE) having a plurality of antenna ports is described.The non-transitory computer-readable medium may include instructionsoperable to cause a processor to identify a compatibility of at leastone antenna port combination of the plurality of antenna ports forcoincident use by the UE, transmit a message to a base stationindicating whether two or more antenna ports are available forcoincident use based at least in part on the identified compatibility,and communicate with the base station via at least one of the pluralityof antenna ports. The at least one of the plurality of antenna ports maybe selected based at least in part on the identified compatibility.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for determining a delay constraintbetween using antenna ports in the at least one antenna portcombination. Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting an indication of thedelay constraint in the message to the base station.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the message indicates aplurality of antenna port combinations and corresponding delayconstraints between using antenna ports for each of the plurality ofantenna ports combinations. The delay constraint may indicate a durationof time between using antenna ports in the corresponding antenna portcombination. In some examples of the method, apparatus, andnon-transitory computer-readable medium described above, a zero delayindicates that the at least one antenna port combination is compatiblefor concurrent use and a non-zero delay indicates that the at least oneantenna port combination comprises an antenna port that supports useafter expiry of the delay from use of another antenna port of the atleast one antenna port combination.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a scheduling message fromthe base station indicating an uplink precoder for the at least one ofthe plurality of antenna ports for communicating with the base station.Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for applying the uplink precoder to theat least one of the plurality of antenna ports.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a scheduling message fromthe base station indicating the at least one of the plurality of antennaports. Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a downlink transmissionover the at least one of the plurality of antenna ports. Some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for detecting that the at least one antenna portcombination comprises antenna ports that share a transmit chain, whereinidentifying the compatibility comprises determining that the at leastone antenna port combination is incompatible for coincident use based onthe detection.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for detecting that the at least oneantenna port combination comprises antenna ports with independenttransmit chains. In some examples, identifying the compatibilitycomprises determining that the at least one antenna port combination iscompatible for coincident use based on the detection. Some examples ofthe method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for determining a ratio of transmit chains to physicalantennas for the at least one antenna port combination, wherein theidentifying is based on the ratio.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for detecting that a first antenna portand a second antenna port of the at least one antenna port combinationshare a physical antenna. In some examples, identifying thecompatibility comprises determining that the at least one antenna portcombination is compatible for coincident use based on the detection.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for detecting that a first antenna portand a second antenna port of the at least one antenna port combinationdo not share a physical antenna. In some examples, identifying thecompatibility comprises determining that the at least one antenna portcombination is incompatible for coincident use based on the detection.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for detecting that a number of physicalantennas associated with the at least one antenna port combination areco-located on an antenna panel. In such examples, identifying thecompatibility is based on the detection.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the message comprises acompatible port set indicating that two or more antenna ports areavailable for concurrent use. In some examples of the method, apparatus,and non-transitory computer-readable medium described above, thecompatibility of compatible port set is indicated via a bit-map ormatrix.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the message comprises anincompatible port set indicating that the at least one antenna portcombination is incompatible for concurrent use. In some examples of themethod, apparatus, and non-transitory computer-readable medium describedabove, the message comprises a compatible port set indicating a firstset of antenna port combinations that are compatible for concurrent useand an incompatible port set indicating a second set of antenna portcombinations that are incompatible for concurrent use.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the message may include anindication of a number of antenna ports available for coincident use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationthat supports Antenna port compatibility signaling in accordance withaspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system thatsupports antenna port compatibility signaling in accordance with aspectsof the present disclosure.

FIG. 3 illustrates an example of a transmitter that supports antennaport compatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 4 illustrates an example of a receiver that supports antenna portcompatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 5 illustrates an example of a user equipment that supports antennaport compatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 6 illustrates an example of a process flow that supports antennaport compatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 7 illustrates an example of a process flow for antenna portcompatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 8 shows a block diagram of a device that supports antenna portcompatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 9 shows a block diagram of a device that supports antenna portcompatibility signaling in accordance with aspects of the presentdisclosure.

FIG. 10 illustrates a block diagram of a system including a UE thatsupports antenna port compatibility signaling in accordance with aspectsof the present disclosure.

FIGS. 11 through 13 illustrate methods for antenna port compatibilitysignaling in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless communications may involve a user equipment (UE) usingmultiple antenna ports concurrently. For example, in New Radio (NR), aUE may use multiple antenna ports (e.g., uplink transmission ports)concurrently to send multiple precoded sounding reference signals (SRS)on the same symbol. Or the UE may use multiple antenna ports at oncewhen communicating over multiple layers (e.g., rank >1) usingmultiple-input-multiple-output (MIMO) techniques. In some cases, a UE'simplementation or design may constrain which antenna ports can be usedat the same time, if any, and thus whether any two or more antenna portsmay be available for coincident use. For example, some antenna ports maynot be used together if they share a transmit chain. Also, somecombinations of antenna ports may not support concurrent use if thenumber of transmit chains is greater than the number of physicalantennas associated with the antenna ports. For a combination of antennaports that cannot be used concurrently, there may be constraints on thetime needed between using the antenna ports in the combination. Forexample, in a two-port combination, there may be a delay in betweenusing the first port and using the second port.

If a base station scheduling a UE is unaware that the UE is subject tosuch constraints, the base station may attempt to schedule the UE in amanner that cannot be implemented by the UE. For example, the basestation may schedule the UE to communicate concurrently over acombination of antenna ports that do not support concurrent use.Additionally or alternatively, the base station may schedule the UE in amanner that fails to take advantage of the UE's ability to communicateover some antenna ports concurrently. For example, the base station mayschedule (e.g., in a reference signal configuration message) the UE totransmit multiple SRS across several different transmit time intervals(TTIs), rather than in the same TTI. Thus, a base station's lack ofknowledge of the UE's capabilities may impair communications and reduceefficiency.

According to the techniques described herein, a UE may determine whichcombinations of its antenna ports are compatible for concurrent use andwhich are not. The UE may send this information to a serving basestation. For example, the UE may send a message that indicates a) theantenna port combinations that are compatible for concurrent use and/orb) the antenna port combinations that are incompatible for concurrentuse. In some examples, the message may indicate a threshold number,where any combination up to the threshold number of antenna ports iscompatible for concurrent use but any combination with more than thethreshold number of antenna ports is not compatible for concurrent use.In some cases, the UE may also convey the delay constraint value foreach combination of antenna ports that is incompatible for concurrentuse. However, the UE may refrain from sending extraneous information tothe serving base station, such as the implementation details whichcaused the constraints to arise. For example, the UE may refrain fromsending the base station indications of the antenna-to-port mapping usedby the UE or the number of transmit chains available at the UE.

Based on the information from the UE, the base station may incorporatethe constraints of the UE into its scheduling decisions. For example,the base station may select a precoder for the UE that allows the UE tosimultaneously use a combination of antenna ports that are compatiblefor concurrent use. In another example, the base station may avoidselecting a precoder for the UE that requires the UE to simultaneouslyuse a combination of antenna ports that are incompatible for concurrentuse. The base station may make these selections without knowing theimplementation details associated with the UE's constraints.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE), LTE-Advanced (LTE-A) network, ora New Radio (NR) network. In some cases, wireless communications system100 may support enhanced broadband communications, ultra-reliable (i.e.,mission critical) communications, low latency communications, andcommunications with low-cost and low-complexity devices. A UE 115 may becapable of communicating using multiple antenna ports, but not allcombinations of antenna ports may be support simultaneous use. A UE 115may determine which antenna port combinations are compatible forconcurrent use and indicate these combinations to a base station 105.The base station 105 may take the compatibly of the antenna ports intoaccount when scheduling communications with the UE 115.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink transmissions from a UE 115 to a base station 105, ordownlink transmissions, from a base station 105 to a UE 115. Controlinformation and data may be multiplexed on an uplink channel or downlinkaccording to various techniques. Control information and data may bemultiplexed on a downlink channel, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, the controlinformation transmitted during a transmission time interval (TTI) of adownlink channel may be distributed between different control regions ina cascaded manner (e.g., between a common control region and one or moreUE-specific control regions).

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as evolved NodeBs (eNBs) 105.

A base station 105 may be connected by an S1 interface to the corenetwork 130. The core network may be an evolved packet core (EPC), whichmay include at least one mobility management entity (MME), at least oneserving gateway (S-GW), and at least one Packet Data Network (PDN)gateway (P-GW). The MME may be the control node that processes thesignaling between the UE 115 and the EPC. All user Internet Protocol(IP) packets may be transferred through the S-GW, which itself may beconnected to the P-GW. The P-GW may provide IP address allocation aswell as other functions. The P-GW may be connected to the networkoperators IP services. The operators IP services may include theInternet, the Intranet, an IP Multimedia Subsystem (IMS), and aPacket-Switched (PS) Streaming Service.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile station, a subscriber station, a mobile unit, asubscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology. A UE 115 may alsobe a cellular phone, a personal digital assistant (PDA), a wirelessmodem, a wireless communication device, a handheld device, a tabletcomputer, a laptop computer, a cordless phone, a personal electronicdevice, a handheld device, a personal computer, a wireless local loop(WLL) station, an Internet of Things (IoT) device, an Internet ofEverything (IoE) device, a machine type communication (MTC) device, anappliance, an automobile, or the like.

UEs 115 may include a communication manager, which may facilitateantenna port compatibility signaling. A UE 115 may include multipleantenna ports (e.g., uplink transmission ports and downlink transmissionports) associated with a number of physical antennas. Although somecombinations of the antenna ports may be used concurrently, theimplementation or design of a UE 115 may prevent other combinations ofantenna ports from being used concurrently. For example, the number oftransmit chains, or their connection to the UE's physical antennas, maylimit which combinations of antenna ports can be used concurrently.

If a base station 105 is unaware of a UE's analog beamformingconstraints, the base station 105 may inefficiently schedule the UE 115for communications, or schedule the UE 115 for communications that theUE 115 does not support. In an example of inefficient scheduling, thebase station 105 may schedule the UE 115 (e.g., in a reference signalconfiguration message) to send multiple sounding reference signals (SRS)over a corresponding number of symbols when the UE 115 could have sentthe SRS over a single symbol by using multiple antenna ports at once. Inan example of unsupported scheduling, the base station 105 may schedulethe UE 115 to send multiple SRS concurrently over a combination ofantenna ports that are not compatible with concurrent use (e.g., thebase station 105 may direct the UE 115 to use a precoder that the UE 115does not support).

According to the techniques described herein, a UE 115 may identify thecompatibility of multiple combinations of antenna ports for coincidentuse. As used herein, coincident use refers to concurrent use and/or usewithin a given delay threshold. A combination of antenna ports may becompatible for coincident use if the antenna ports in the combinationcan be used concurrently or proximately (e.g., one at a time after adelay has elapsed in between use). Additionally or alternatively, the UE115 may identify which combinations of antenna ports are incompatiblefor concurrent or coincident use. The UE 115 may report thecompatibility of the antenna port combinations to a base station 105.However, the UE 115 may not report the implementation details of theUE's transmit chains and physical antennas to the base station 105.Thus, overhead signaling may be reduced and the implementation detailsof the transmit chains and physical antennas may be transparent to thebase station 105. Using the compatibility information from the UE 115,the base station 105 may schedule communications with the UE 115 thatavoid improper use of incompatible antenna port combinations but takeadvantage of compatible antenna port combinations.

Wireless communications system 100 may operate in an ultra-highfrequency (UHF) frequency region using frequency bands from 700 MHz to2600 MHz (2.6 GHz), although some networks (e.g., a wireless local areanetwork (WLAN)) may use frequencies as high as 4 GHz. This region mayalso be known as the decimeter band, since the wavelengths range fromapproximately one decimeter to one meter in length. UHF waves maypropagate mainly by line of sight, and may be blocked by buildings andenvironmental features. However, the waves may penetrate wallssufficiently to provide service to UEs 115 located indoors. Transmissionof UHF waves is characterized by smaller antennas and shorter range(e.g., less than 100 km) compared to transmission using the smallerfrequencies (and longer waves) of the high frequency (HF) or very highfrequency (VHF) portion of the spectrum.

In some cases, wireless communications system 100 may also utilizeextremely high frequency (EHF) portions of the spectrum (e.g., from 30GHz to 300 GHz). This region may also be known as the millimeter band,since the wavelengths range from approximately one millimeter to onecentimeter in length. Thus, EHF antennas may be even smaller and moreclosely spaced than UHF antennas. In some cases, this may facilitate useof antenna arrays within a UE 115 (e.g., for directional beamforming).However, EHF transmissions may be subject to even greater atmosphericattenuation and shorter range than UHF transmissions.

Thus, wireless communications system 100 may support millimeter wave(mmW) communications between UEs 115 and base stations 105. Devicesoperating in mmW or EHF bands may have multiple physical antennas toallow beamforming. That is, a base station 105 may use multiple antennasor antenna arrays to conduct beamforming operations for directionalcommunications with a UE 115. Beamforming (which may also be referred toas spatial filtering or directional transmission) is a signal processingtechnique that may be used at a transmitter (e.g., a base station 105)to shape and/or steer an overall antenna beam in the direction of atarget receiver (e.g., a UE 115). This may be achieved by combiningelements in an antenna array in such a way that transmitted signals atparticular angles experience constructive interference while othersexperience destructive interference.

Multiple-input multiple-output (MIMO) wireless systems use atransmission scheme between a transmitter (e.g., a base station 105) anda receiver (e.g., a UE 115), where both transmitter and receiver areequipped with multiple antennas. Some portions of wirelesscommunications system 100 may use beamforming. For example, base station105 may have an antenna array with a number of rows and columns ofantenna ports that the base station 105 may use for beamforming in itscommunication with UE 115. Signals may be transmitted multiple times indifferent directions (e.g., each transmission may be beamformeddifferently). A mmW receiver (e.g., a UE 115) may try multiple beams(e.g., antenna subarrays) while receiving the synchronization signals.

In some cases, the physical antennas of a base station 105 or UE 115 maybe located within one or more antenna arrays, which may supportbeamforming or MIMO operation. One or more base station antennas orantenna arrays may be collocated at an antenna assembly, such as anantenna tower. In some cases, antennas or antenna arrays associated witha base station 105 may be located in diverse geographic locations. Abase station 105 may multiple use antennas or antenna arrays to conductbeamforming operations for directional communications with a UE 115.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit (which may be a sampling period of T_(s)=1/30,720,000seconds). Time resources may be organized according to radio frames oflength of 10 ms (T_(f)=307200 T_(s)), which may be identified by asystem frame number (SFN) ranging from 0 to 1023. Each frame may includeten 1 ms subframes numbered from 0 to 9. A subframe may be furtherdivided into two 0.5 ms slots, each of which contains 6 or 7 modulationsymbol periods (depending on the length of the cyclic prefix prependedto each symbol). Excluding the cyclic prefix, each symbol contains 2048sample periods. In some cases the subframe may be the smallestscheduling unit, also known as a TTI. In other cases, a TTI may beshorter than a subframe or may be dynamically selected (e.g., in shortTTI bursts or in selected component carriers using short TTIs).

A resource element may consist of one symbol period and one subcarrier(e.g., a 15 KHz frequency range). A resource block may contain 12consecutive subcarriers in the frequency domain and, for a normal cyclicprefix in each OFDM symbol, 7 consecutive OFDM symbols in the timedomain (1 slot), or 84 resource elements. The number of bits carried byeach resource element may depend on the modulation scheme (theconfiguration of symbols that may be selected during each symbolperiod). Thus, the more resource blocks that a UE receives and thehigher the modulation scheme, the higher the data rate may be.

Wireless communications system 100 may support operation on multiplecells or carriers, a feature which may be referred to as carrieraggregation (CA) or multi-carrier operation. A carrier may also bereferred to as a component carrier (CC), a layer, a channel, etc. Theterms “carrier,” “component carrier,” “cell,” and “channel” may be usedinterchangeably herein. A UE 115 may be configured with multipledownlink CCs and one or more uplink CCs for carrier aggregation. Carrieraggregation may be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including: wider bandwidth, shorter symbol duration, shorterTTIs, and modified control channel configuration. In some cases, an eCCmay be associated with a carrier aggregation configuration or a dualconnectivity configuration (e.g., when multiple serving cells have asuboptimal or non-ideal backhaul link). An eCC may also be configuredfor use in unlicensed spectrum or shared spectrum (where more than oneoperator is allowed to use the spectrum). An eCC characterized by widebandwidth may include one or more segments that may be utilized by UEs115 that are not capable of monitoring the whole bandwidth or prefer touse a limited bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration isassociated with increased subcarrier spacing. A device, such as a UE 115or base station 105, utilizing eCCs may transmit wideband signals (e.g.,20, 40, 60, 80 MHz, etc.) at reduced symbol durations (e.g., 16.67microseconds). A TTI in eCC may consist of one or multiple symbols. Insome cases, the TTI duration (that is, the number of symbols in a TTI)may be variable.

A shared radio frequency spectrum band may be utilized in an NR sharedspectrum system. For example, an NR shared spectrum may utilize anycombination of licensed, shared, and unlicensed spectrums, among others.The flexibility of eCC symbol duration and subcarrier spacing may allowfor the use of eCC across multiple spectrums. In some examples, NRshared spectrum may increase spectrum utilization and spectralefficiency, specifically through dynamic vertical (e.g., acrossfrequency) and horizontal (e.g., across time) sharing of resources.

In some cases, wireless system 100 may utilize both licensed andunlicensed radio frequency spectrum bands. For example, wireless system100 may employ LTE License Assisted Access (LTE-LAA) or LTE Unlicensed(LTE U) radio access technology or NR technology in an unlicensed bandsuch as the 5 Ghz Industrial, Scientific, and Medical (ISM) band. Whenoperating in unlicensed radio frequency spectrum bands, wireless devicessuch as base stations 105 and UEs 115 may employ listen-before-talk(LBT) procedures to ensure the channel is clear before transmittingdata. In some cases, operations in unlicensed bands may be based on a CAconfiguration in conjunction with CCs operating in a licensed band.Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, or both. Duplexing in unlicensed spectrum may bebased on frequency division duplexing (FDD), time division duplexing(TDD) or a combination of both.

FIG. 2 illustrates an example of a wireless communications system 200for antenna port compatibility signaling in accordance with variousaspects of the present disclosure. Wireless communications system 200includes base station 105-a and UE 115-a, which may be examples of thecorresponding devices described with reference to FIG. 1. Base station105-a may communicate with wireless devices inside coverage area 110-a;for example, base station 105-a may communicate with UE 115-a over awireless channel via a communication link. Base station 105-a and UE115-a may be capable of communicating over multiple antenna portssimultaneously. According to the techniques described herein, UE 115-amay inform base station 105-a of the antenna ports that supportsimultaneous communication and/or of those that do not.

Base station 105-a may include multiple antennas 205 (e.g., n antennas).For example, base station 105-a may include antenna 205-a, antenna205-b, and antenna 205-c. UE 115-a may also include multiple antennas210. For example, UE 115-a may include antenna 210-a, 210-b, and 210-c.Each antenna may be coupled with processing circuitry, which may includeone or more transmit chains and/or one or more receive chains. Althoughshown with the same number of antennas, base station 105-a and UE 115-amay include different numbers of antennas. In some cases, an antenna maybe associated with multiple transmit or receive chains, or multipleantennas may share a transmit or receive chain. UE 115-a may definemultiple antenna ports, which may be mapped to precoders that areassociated with multiple physical antennas 210.

In some cases, UE 115-a may employ MIMO techniques in which UE 115-auses multiple antenna ports to receive communications from base station105-a, which also uses multiple antenna ports to transmit. MIMO may usea technique called spatial division multiplexing that takes advantage ofthe multiple transmit and receive chains to send multiple streams ofdata simultaneously on the same wireless channel, thereby increasingdata rate and overall throughput. In some cases, base station 105-aand/or UE 115-a may use beamforming to send a MIMO transmission. Forexample, base station 105-a may send a beamformed transmission 215 to UE115-a. Prior to sending a beamformed transmission over a channel, basestation 105-a may gather information about the channel. Base station105-a (as beamformer) may use the information to determine a beamformingsteering matrix that is used to direct transmissions towards the UE asthe target device(s). The transmissions may be directed by applyingweights to antennas within an antenna array (e.g., as defined by thebeamforming matrix) so that constructive and destructive interferencefocuses the energy of the transmission in a particular direction.

In some cases, an application may call for multiple antenna ports (e.g.,multiple uplink transmission ports) to be used at once. For example,base station 105-a may instruct UE 115-a to send multiple precoded SRSon the same symbol. Or multiple antenna ports may be used simultaneouslyto implement uplink MIMO with rank >1 (e.g., multiple layers). But someor all antenna ports may not be configured for simultaneous use.According to the techniques described herein, UE 115-a may determinewhich antenna ports support simultaneous use and send a message thatindicates these antenna ports to base station 105-a. In some examples,the message may include an indication of a number of antenna portsavailable for coincident use. For example, the message may include anindication that no antenna ports are available for coincident use, anindication that two antenna ports are available for coincident use, oran indication that some other number of antenna ports are available forcoincident use. Based on the antenna port information, base station105-a may assign scheduling resources and precoders to UE 115-a. UE115-a may communicate according to the scheduling assignment(s) frombase station 105-a.

FIG. 3 illustrates an example of a transmitter 300 for use in antennaport compatibility signaling in accordance with various aspects of thepresent disclosure. Transmitter 300 may be part of a base station 105 orUE 115, which may be examples of the corresponding devices describedwith reference to FIG. 1. Transmitter 300 may be part of a transceiverthat includes a receiver with which the transmitter may share a numberof physical antennas 315. The physical antennas 315 may be associatedwith antenna ports, some of which may be constrained from concurrent usedue to, e.g., shared processing circuitry such as transmit chains 320. AUE 115 may detect which combinations of antenna ports are prohibitedfrom concurrent use (e.g., incompatible for simultaneous use) and reportthese combinations to a base station 105. Additionally or alternatively,the UE 115 may detect which antenna port combinations are compatible forconcurrent use and report these combinations to the base station 105.

Transmitter 300 may include two pairs of physical antennas 315, each ofwhich may share a different transmit chain 320. For example, antenna315-a and antenna 315-b may share transmit chain 320-a and antenna 315-cand antenna 315-d may share transmit chain 320-b. Thus, four physicalantennas 315 may be managed using two transmit chains 320. A transmitchain 320 may connect to one physical antenna 315 at a time viaswitching circuitry 325 (e.g., transmit chain 320-a may switch betweenphysical antennas 315-a and 315-b and transmit chain 320-b may switchbetween physical antennas 315-c and 315-d). Because the transmit chains320 are shared, simultaneous use of physical antennas 315-a and 315-b isnot supported and simultaneous use of physical antennas 315-c and 315-dis not supported. For example, when transmit chain 320-a is connected tophysical antenna 315-a, simultaneous connection to physical antenna315-b is not supported. Although two pairs of two physical antennas 315are shown, any number of physical antennas may be included intransmitter 300. Similarly, any number of transmit chains 320 may beused and the relationship between the transmit chains 320 and thephysical antennas may vary.

An antenna port may be defined by coefficients (e.g., complex weights)applied to one or more physical antennas. For example, a port may bedefined as [u1 0 u2 0], where ‘u1’ is the complex weight applied tophysical antenna 315-a and ‘u2’ is the complex weight applied tophysical antenna 315-c (in this example a complex weight of zero isapplied to physical antennas 315-b and 315-d). A transmitter 300 mayapply precoding for a signal to be transmitted via one or more ports viaa precoder 330. The complex weights for the physical antennas accordingto the antenna ports may be applied by the transmit chains 320 or theprecoder 3330. For example, precoder 330 may apply a precoder such as [a0 b 0] to a combination of fours ports (e.g., port 1, port 2, port 3,and port 4), which means that a precoding weight ‘a’ is applied to port1, a precoding weight ‘b’ is applied to port 3, and no precoding weightis applied to ports 2 and 4. The precoder 330 and/or the transmit chains320 may then apply the complex weights assigned to each physical antennafor the antenna ports. Thus, an antenna port may be mapped to a precoderand may involve more than one physical antenna 315. The beamforming andprecoding weights may be real or complex and may be selected tofacilitate beamforming and/or MIMO communications.

In some cases, the antenna ports that are supported by a transmitter 300may be constrained by the configuration of the transmitter 300 (e.g.,sharing the transmit chains 320 between multiple physical antennas 315may preclude some antenna ports from being used concurrently orcoincidently). For instance, an antenna port of [u1 u2 0 0] is notsupported by the transmitter 300 because the antenna port requiresphysical antennas 315-a and 315-b to be used concurrently, which is notpossible given the limitations of transmit chain 320-a. Similarly, anantenna port [0 0 u1 u2] may not be supported by the transmitter 300because it requires concurrent use of physical antennas 315-c and 315-d,which cannot be used simultaneously.

The configuration of transmitter 300 may also impose constraints onwhich antenna ports are compatible for simultaneous use. For example,antenna port [u1 0 0 0] may be used simultaneously with antenna port [00 0 u2] (because the combination involves physical antennas 315-a and315-c) but not antenna port [0 u2 0 0] (because the combination involvesphysical antennas 315-a and 315-b). Accordingly, precoder [a 0 0 b] maybe supported by transmitter 300 but precoder [a b 0 0] may not besupported by transmitter 300 (because precoder [a b 0 0] ultimatelyapplies precoding weights ‘a’ and ‘b’ to physical antennas 315-a and315-b, which cannot be used simultaneously). Thus, a UE 115 maydetermine which antenna ports support simultaneous use by evaluating theconnectivity between the associated physical antennas 315 and transmitchains 320. Because a UE 115 may be constrained from using certainantenna ports at all, or certain combinations of antenna portsconcurrently, a UE 115 may be prevented from arbitrarily applyingbeamforming or precoding weights to the four physical antennas 315.

According to the techniques described herein, a UE 115 may detect (e.g.,by evaluating the hardware configuration of transmitter 300) whethercertain physical antennas 315 can be used concurrently, if any, and thuswhether two or more antenna ports are available for coincident use. Forexample, the UE 115 may detect that the following pairs of physicalantennas can be used concurrently: 315-a and 315-c, 315-a and 315-d,315-b and 315-c, and 315-b and 315-d. The UE 115 may also detect thatcertain physical antennas 315 cannot be used concurrently (e.g., 315-aand 315-b, 315-c and 315-d). In some cases, the UE 115 may indicate tothe base station which pairs of physical antennas 315 are compatible forconcurrent use and/or which pairs of physical antennas 315 areincompatible for concurrent use. The UE 115 may use the physical antennainformation to determine that certain antenna ports are not availablefor use by the UE 115 and may report these ports to a base station 105.For example, the UE 115 may send a message to the base station 105indicating that port [u1 u2 0 0] and port [0 0 u1 u2] are not supportedby the UE 115. Additionally or alternatively, the UE 115 may send amessage to the base station 105 indicating the antenna ports that aresupported by the UE 115 (e.g., antenna ports [u1 0 0 u2], [u1 0 u2 0],[0 u1 u2 0], and [0 u10 u2]). A base station may use the antenna portinformation to identify precoders that are not supported by the UE 115(e.g., precoder [a b 0 0]).

The UE 115 may also detect that certain antenna port combinations do notsupport concurrent use and may report these combinations to the basestation 105. For example, the UE 115 may send a message to the basestation 105 indicating that antenna port combination [u1 0 u2 0] cannotbe used concurrently with antenna port combination [0 v1 0 v2].Additionally or alternatively, the UE 115 may send a message to the basestation 105 indicating the antenna ports that are compatible forconcurrent use. After informing the base station 105 of thecompatibility of antenna port combinations, the UE 115 may receivescheduling information from the base station 105. The schedulinginformation may include which precoder to use for an uplinktransmission. The UE 115 may apply the precoder to the appropriate portsand simultaneously send signals to the base station 105 over thephysical antennas 315 corresponding to those ports.

In some cases, a UE 115 may determine that a combination of antennaports supports proximate use (e.g., even if they do not supportconcurrent use). For example, UE 115 may determine that antenna port [u10 u2 0] can be used after antenna port [0 v10 v2] if an appropriateduration of time has elapsed in between use. The duration of time may bea delay constraint (e.g., the minimum delay or duration of time requiredby the UE 115 between use of the antenna ports) that is based onhardware limitations associated with switching between the two antennaports. In some examples, the UE 115 may send a message to the basestation 105 indicating a) the combination of antenna ports that supportsproximate use and b) the corresponding delay associated with thatcombination of antenna ports, where a zero delay may mean that theantenna port combination can be used concurrently. The base station 105may take this information into account when making scheduling decisionsfor the UE 115.

FIG. 4 illustrates an example of a receiver 400 for use in antenna portcompatibility signaling in accordance with various aspects of thepresent disclosure. Receiver 400 may be part of a base station 105 or UE115, which may be examples of the corresponding devices described withreference to FIG. 1. Receiver 400 may be part of a transceiver, whichmay include a transmitter such as transmitter 300. Receiver 400 mayinclude a number of physical antennas 315 that may be associated withantenna ports, some of which may be constrained from concurrent use dueto, e.g., shared processing circuitry such as receive chains 320. A UE115 may detect which combinations of antenna ports are prohibited fromconcurrent use (e.g., incompatible for simultaneous use) and reportthese combinations to a base station 105. Additionally or alternatively,the UE 115 may detect which antenna port combinations are compatible forconcurrent use and report these combinations to the base station 105.

Receiver 400 may include physical antenna 315-e and physical antenna315-f, which share receive chain 405-a, and physical antenna 315-g andphysical antenna 315-h, which share receive chain 405-b. The receivechains 405 may receive signals from the physical antennas 315, processaspects of those signals, and pass them on to processing module 410 forfurther processing (e.g., decoding, demodulation, etc.). Using switchingcircuitry 415, receive chain 405-a may switch between physical antennas315-e and 315-f and receive chain 405-b may switch between physicalantennas 315-g and 315-h. Because the receive chains 405 are shared,simultaneous use of physical antennas 315-e and 315-f is not supportedand simultaneous use of physical antennas 315-g and 315-h is notsupported.

A UE 115 may detect which physical antennas 315 can be usedsimultaneously and report this information to a base station 105.Additionally or alternatively, the UE 115 may use this information todetermine which antenna ports are supported by receiver 400, and ofthese which can be used concurrently. The UE 115 may report this antennaport compatibility information to the base station 105. For example, theUE 115 may indicate a set of antenna port combinations that arecompatible for concurrent use and thus indicate that two or more antennaports are available for coincident use. Additionally or alternatively,the UE 115 may indicate a set of antenna port combinations that areincompatible for concurrent use. In some cases, the UE 115 may decidewhich set to send to the base station 105 based on how many resourceseach set would consume. For example, the UE 115 may send theincompatible port set if transmitting the incompatible port set consumesless resources than transmitting the compatible port set. The basestation 105 may schedule communications with the UE 115 based on theantenna port compatibility information from the UE 115.

FIG. 5 illustrates an example of UE 500 for antenna port compatibilitysignaling in accordance with various aspects of the present disclosure.UE 500 may be an example of a UE 115 described with reference to FIG. 1.UE 500 may include multiple transmit chains 320, which may be examplesof a transmit chain 320 described with reference to FIG. 3. UE 500 alsoincludes physical antenna 315-i, physical antenna 315-j, physicalantenna 315-k, and physical antenna 315-l. Any transmit chain 320 can beconnected to any one physical antenna 315 at a time via multiplexor 510.Physical antenna 315-i and physical antenna 315-j may be co-located onantenna panel 505-a and physical antenna 315-k and physical antenna315-l may be co-located on antenna panel 505-b. An antenna panel 505 mayinclude a number of physical antennas 315, which may be in closephysical proximity. In some instances, the physical antennas 315 on apanel may share a digital signal input (e.g., via a digital-to-analogconverter (DAC)), but may have separate analog beamforming capabilities(independently applied analog beam weights). Thus, an antenna panel 505may be used to perform analog beamforming. However, physical antennas315 on an antenna panel 505 may not have independent digital beamformingor have independent precoders applied.

For UE 500, four ports may be defined over the four physical antennas315: port 1 (e.g., [u1 u2 0 0]), port 2 (e.g., [0 0 v1 v2]), port 3(e.g., [0 w1 0 w2]), and port 4 (e.g., [x1 0 x2 0]). Each beamformingweight in a port may correspond to a physical antenna 315. In thisexample, the first beamforming weight corresponds to physical antenna315-i, the second beamforming weight corresponds to physical antenna315-j, the third beamforming weight corresponds to physical antenna315-k, and the fourth beamforming weight corresponds to physical antenna315-l.

While some combinations of the four defined ports may be usedconcurrently, others may be precluded from simultaneous use due to theratio of transmit chains 320 to physical antennas 315. This is because aseparate transmit chain 320 must be assigned to a physical antenna 315in order to apply a unique beamforming weight to that physical antenna315. Thus, when only one transmit chain 320 is available, none of thefour defined ports are supported by the UE 500 (because each port usestwo physical antennas 315). When two transmit chains 320 are available,such as transmit chain 320-c and transmit chain 320-d, the four definedantenna ports are supported by the UE 500 but they can only be used oneat a time (e.g., not concurrently), and thus no two or more antennas maybe available for coincident use. Put another way, when two of thedefined transmit chains 320 are available, only one antenna port usingtwo physical antennas can be used at a time since each port uses twophysical antennas. When three transmit chains 320 are used, any two ofthe defined antenna ports that share a physical antenna 315 can be usedconcurrently. When four transmit chains 320 are available, any two ofthe defined antenna ports can be used concurrently. Thus, a UE 500 mayevaluate the ratio of transmit chains to physical antennas whendetermining whether antenna port combinations support concurrent use. Ifthe ratio of transmit chains to physical antennas is less than 1, UE 500may determine which antenna port combinations support concurrent use bydetermining whether any of the antenna ports in a combination share aphysical antenna.

For example, when three transmit chains 320 are used (e.g., transmitchain 320-c, transmit chain 320-d, and transmit chain 320-e), port 1 andport 3 can be used concurrently because they share physical antenna315-j. Port 1 and port 4 can be used concurrently because they sharephysical antenna 315-i. Port 2 and port 3 can be used concurrentlybecause they share physical antenna 315-l. And port 2 and port 4 can beused concurrently because they share physical antenna 315-k. However,port 1 and port 2 cannot be used concurrently and port 3 and port 4cannot be used concurrently because they do not share a physical antenna315. Thus, UE 500 may simultaneously use two antenna ports withdifferent precoders as long as the two ports share at least one physicalantenna 315.

According to the techniques described herein, UE 500 may determine thatthe ratio of transmit chains 320 to physical antennas 315 preventssimultaneous use of certain antenna ports and report that finding to abase station 105. For example, UE 500 may transmit a message (e.g., anantenna port compatibility message) to the base station 105 thatindicates which of the defined antenna ports can be used concurrentlyand which cannot be used concurrently. In some cases, the UE 500 mayinclude a delay constraint with each antenna port combination. The delayconstraint may indicate a minimum duration of time for the UE 500between use of one of the antenna ports and use of any other antennaport in the antenna port combination.

The base station 105 that receives the antenna port compatibilitymessage may learn which combinations are compatible for concurrent useand which are not. Based on this information, the base station 105 mayselect an uplink precoder to be applied to the antenna ports defined forUE 115-b. For example, base station 105 may select uplink precoder [a 0b 0], which is supported because antenna port 1 and antenna port 3 arecompatible for concurrent use. The base station 105 may avoid selectingan uplink precoder that requires concurrent use of antenna ports thatare incompatible for concurrent use (e.g., the base station 105 mayavoid selecting uplink precoder [a b 0 0], which requires concurrent useof antenna port 1 and antenna port 2).

In some cases, UE 500 may detect that several physical antennas 315 areco-located on the same antenna panel 505. For example, UE 500 may detectthat physical antenna 315-i and physical antenna 315-j are both onantenna panel 505-a. UE 500 may also detect that physical antenna 315-kand physical antenna 315-l are both on antenna panel 505-b. Because thephysical antennas 315 on an antenna panel 505 share the same analogbeamforming, the physical antennas 315 may not support simultaneoustransmission or reception of two different analog beams. However,physical antennas 315 on different antenna panels 505 may supportsimultaneous transmission or reception of two different analog beams.Thus, a UE 115 with only one antenna panel 505 may not supportsimultaneous communication using two different analog beams, but a UE115 with multiple antenna panels 505 (e.g., like UE 500) may be able tocommunicate in such a manner (providing the analog beams are sent usingphysical antennas 315 that are on different antenna panels 505). UE 500may determine which antenna port combinations can be used concurrentlybased on the location of their associated physical antennas and reportthat information to a base station 105. Thus, the UE 500 may inform thebase station 105 about constraints in analog beamforming capabilities.

In the millimeter wave context, the UE 500 may send capabilityinformation (to the base station 105) that applies to specific beams orbeam identifiers (IDs) that may or may not be compatible with eachother. For example, UE 500 may sound a channel using two different beamsat different times, but depending on the implementation, the UE 500 mayor may not be able to support simultaneous use of both beams duringsubsequent data transmissions. For instance, if the two beams requirethe use of two different panels 505 that share the same transmit chain320 or power amplifier, this may restrict the UE 500 to using only oneof the panels 505 (and hence only one of the beams) at a given time. Inthis case, the UE 500 may update the base station 105 accordingly usinga capability indication that specifies a compatible beam ID set or anincompatible beam ID set.

FIG. 6 illustrates an example of a process flow 600 for antenna portcompatibility signaling in accordance with various aspects of thepresent disclosure. Process flow 600 may include base station 105-b andUE 115-b. UE 115-b may include a number of physical antennas, transmitchains, and receive chains, and may be associated with multiple antennaports.

At 605, UE 115-b may identify combinations of antenna ports forcommunication with base station 105-b. At 610, UE 115-b may determinewhich of the combinations are compatible for coincident use (e.g.,concurrent or proximate use). At 615, UE 115-b may transmit acompatibility message to base station 105-b indicating the compatibilityof the various antenna port combinations. In some cases, thecompatibility message includes a compatible port set. The compatibleport set may indicate which combinations of antenna ports are compatiblefor concurrent use (e.g., which antenna ports can be usedsimultaneously) and thus that two or more antenna ports are availablefor coincident use. Additionally or alternatively, the compatibilitymessage may include an incompatible port set (e.g., the message mayinclude a combination of compatible and incompatible sets).Additionally, the compatibility message may indicate the combinations ofantenna ports that are not compatible for concurrent use but thatsupport proximate use. For example, the compatibility message mayinclude a delay constraint value for each combination of antenna ports.The delay constraint value may indicate the duration of time UE 115-bmust wait in between using the antenna ports in the combination. In sucha scenario, the delay value may be zero for antenna port combinationsthat support concurrent use and non-zero for antenna port combinationsthat support proximate use but not concurrent use.

In some cases, the compatibility message may convey the compatibility ofthe antenna port sets in a bit-map. The bit-map may indicate whether anantenna port belongs to the compatible port set or the incompatible portset. In some examples, UE 115-b may determine how many antenna ports arein each set and transmit an indication of the set with the fewest numberof antenna ports. For example, UE 115-b may transmit an indication ofwhether two or more antenna ports, or some other number of antenna portsare available for concurrent use. In some cases, an indication ofwhether two or more antenna ports are available for concurrent use mayinclude an indication of a number of antenna ports available forconcurrent use (e.g., zero or one, which may mean that only one antennaport may be used at a time and thus that two or more antenna ports arenot available for concurrent use, or some other threshold number ofantenna ports (e.g., two, four, or six), where any number of antennaports up to the threshold number of antenna ports are available forconcurrent use and thus indicating that two or more antenna ports areavailable for concurrent use). In such a scenario, UE 115-b may includean indication in the compatibility message that conveys which set(compatible or incompatible) is being sent. In some examples, thecompatibility message may convey the set (e.g., the compatible orincompatible set) in the form of a binary compatibility matrix. Forexample the ith/jth entry of the matrix may indicate whether port i andport j are compatible. Alternatively, a compatibility matrix may usevalues that indicate the delay constraint between using each antennaport combination, where a zero delay constraint indicates that thecombination supports concurrent use and a positive number indicates adelay (e.g., in TTIs, symbols, slots, microseconds, etc.) between use ofantenna ports of the combination.

At 620, base station 105-b may determine uplink scheduling for UE 115-bbased on the compatibility message. For example, base station 105-b maydetermine which antenna ports are to send SRS simultaneously and whichantenna ports are to send SRS after a delay. Additionally oralternatively, base station 105-b may determine an uplink precoder foruse by UE 115-b. The precoder may be based on the compatibility messageand may indicate the precoding weights that UE 115-b is to apply to itsantenna ports during an uplink transmission. At 625, base station 105-bmay transmit a scheduling message to UE 115-b. The scheduling messagemay include an indication of antenna ports to be used for concurrent SRStransmissions and/or an indication of antenna ports to be used for SRStransmissions separated in time (e.g., the scheduling message may be areference signal configuration message). The scheduling message mayadditionally or alternatively include an indication of the uplinkprecoder. At 630, UE 115-b may receive and process the schedulingmessage sent from base station 105-b. At 635, UE 115-b may transmit anuplink transmission to base station 105 according to the uplink precoder(e.g., UE 115-b may the uplink precoder to an antenna port combination)and/or according to the SRS scheduling information. In some cases, theuplink transmission includes data. In other cases, the uplinktransmission includes SRS.

FIG. 7 illustrates an example of a process flow 700 for antenna portcompatibility signaling in accordance with various aspects of thepresent disclosure. Process flow 700 may include base station 105-c andUE 115-c. UE 115-c may include a number of physical antennas, transmitchains, and receive chains, and may be associated with multiple antennaports.

At 705, UE 115-c may identify combinations of antenna ports forcommunication with base station 105-c. At 710, UE 115-c may determinewhich of the combinations are compatible for coincident use. At 715, UE115-c may transmit a compatibility message to base station 105-cindicating whether two or more antenna ports are available forcoincident use based at least in part on the identified compatibility ofthe various antenna port combinations for coincident use. In some cases,the number of antenna ports available for coincident use (and thuswhether antenna ports are available for coincident use) may differ fordownlink transmissions versus uplink transmissions at a UE may bedifferent for DL vs. UL. For example, UE 115-c may have a differentnumber of transmit chains than receive chains (e.g., two transmit chainsand four receive chains). Accordingly, a compatibility message regardingdownlink transmissions (e.g., a compatibility message 715) maysubstantively differ (e.g., may indicate a different number of antennaports available for coincident use, and thus may differ with respect toindicating whether two or more antenna ports are available forcoincident use) from a compatibility message regarding uplinktransmissions (e.g., a compatibility message 615). At 720, base station105-c may determine downlink scheduling for UE 115-c. For example, basestation 105-c may determine which antenna ports are to be used toreceive a downlink transmission. The downlink scheduling may be based onthe compatibility message.

At 725, base station 105-c may transmit a scheduling message to UE115-c. The scheduling message may include an indication of antenna portsto be used for a subsequent communication from base station 105-c. At730, UE 115-c may receive and process the scheduling message sent frombase station 105-c. At 735, base station 105-c may transmit a downlinktransmission to UE 115-c according to the scheduling information. At740, UE 115-c may receive the downlink transmission from base station105-c according to the scheduling information (e.g., using the antennaports indicated by the scheduling information).

FIG. 8 shows a block diagram 800 of a wireless device 805 that supportsantenna port capability signaling in accordance with aspects of thepresent disclosure. Wireless device 805 may be an example of aspects ofa UE 115 as described herein. Wireless device 805 may include receiver810, communications manager 815, and transmitter 820. Wireless device805 may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to antenna portcompatibility signaling, etc.). Receiver 810 may be an example of areceiver 400 described with reference to FIG. 4. Receiver 810 mayreceive a scheduling message from a base station 105. In some examples,the scheduling message may indicate one or more antenna ports forcommunicating with the base station 105. In some examples, thescheduling message may indicate an uplink precoder for one or moreantenna ports. Receiver 810 may also receive a downlink transmission(e.g., over one or more antenna ports, such as those indicated by thescheduling message). Information may be passed on to other components ofthe device. The receiver 810 may be an example of aspects of thetransceiver 1035 described with reference to FIG. 10. The receiver 810may utilize a single physical antenna or a set of physical antennas asdescribed herein.

Communications manager 815 may be an example of aspects of thecommunications manager 1015 described with reference to FIG. 10.Communications manager 815 may identify a set of antenna portsassociated with the wireless device 805 for communication with a basestation 105. The communications manager 815 may identify thecompatibility of antenna port combinations in the set of antenna portsfor coincident use by the wireless device 805. The communicationsmanager 815 transmit a message to a base station indicating whether twoor more antenna ports are available for coincident use based at least inpart on the identified compatibility of the antenna port combinations.The communications manager 815 may communicate with the base station viaone or more of the antenna ports. The antenna port(s) used forcommunication may be selected based on the identified compatibility.

Communications manager 815 and/or at least some of its varioussub-components may be implemented in hardware, software executed by aprocessor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the communicationsmanager 815 and/or at least some of its various sub-components may beexecuted by a general-purpose processor, a digital signal processor(DSP), an application-specific integrated circuit (ASIC), anfield-programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described in thepresent disclosure.

The communications manager 815 and/or at least some of its varioussub-components may be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations by one or more physical devices. In someexamples, communications manager 815 and/or at least some of its varioussub-components may be a separate and distinct component in accordancewith various aspects of the present disclosure. In other examples,communications manager 815 and/or at least some of its varioussub-components may be combined with one or more other hardwarecomponents, including but not limited to an I/O component, atransceiver, a network server, another computing device, one or moreother components described in the present disclosure, or a combinationthereof in accordance with various aspects of the present disclosure.

Transmitter 820 may transmit signals generated by other components ofthe device. The transmitter 820 may be an example of the transmitter 300described with reference to FIG. 30. In some examples, the transmitter820 may be collocated with a receiver 810 in a transceiver module. Forexample, the transmitter 820 may be an example of aspects of thetransceiver 1035 described with reference to FIG. 10. The transmitter820 may utilize a physical single antenna or a set of physical antennasas described herein. In some cases, the transmitter 820 may receiveinformation from other components of wireless device 805. In someexamples, the transmitter 820 may transmit a message to a base station105 that indicates the compatibility of one or more antenna portcombinations for coincident, concurrent or proximate use.

FIG. 9 shows a block diagram 900 of a wireless device 905 that supportsantenna port compatibility signaling in accordance with aspects of thepresent disclosure. Wireless device 905 may be an example of aspects ofa UE 115 or a wireless device 805 as described with reference to FIG. 8.Wireless device 905 may include receiver 910, communications manager915, and transmitter 920. Wireless device 905 may also include aprocessor. Each of these components may be in communication with oneanother (e.g., via one or more buses).

Receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to antenna portcompatibility signaling, etc.). Information may be passed on to othercomponents of the device. The receiver 910 may be an example of aspectsof the transceiver 1035 described with reference to FIG. 10. Thereceiver 910 may utilize a single physical antenna or a set of physicalantennas associated with antenna ports.

Communications manager 915 may be an example of aspects of thecommunications manager 1015 described with reference to FIG. 10.Communications manager 915 may include antenna port administrator 925,compatibility identifier 930, compatibility signaling coordinator 935,uplink/downlink manager 940, and hardware monitor 945. Each of thesemodules may communicate, directly or indirectly, with one another (e.g.,via one or more buses).

Antenna port administrator 925 may identify a set of antenna portsassociated with the wireless device 905. In some cases, antenna portadministrator 925 identify a combination of antenna ports or receive anindication of a combination of antenna ports (e.g., from compatibilityidentifier 930). Antenna port administrator 925 may determine a delaybetween using antenna ports in the antenna port combination (e.g., byevaluating the hardware configuration of receiver 910 or transmitter920). A zero delay may indicate that the antenna port combination iscompatible for concurrent use. A non-zero delay may indicate that theantenna port combination includes a first antenna port that supports useafter expiry of the delay from use of a second antenna port in thecombination.

Compatibility identifier 930 may identify a compatibility of antennaport combinations for coincident use by the wireless device 905.Compatibility identifier 930 may detect that two antenna ports (e.g., afirst antenna port and a second antenna port) in an antenna portcombination share a physical antenna. Compatibility identifier 930 maydetermine that the antenna port combination is compatible for coincidentuse based on the detection that the two ports share a physical antenna.In some cases, compatibility identifier 930 may detect that two antennaports (e.g., a first antenna port and a second antenna port) in anantenna port combination do not share a physical antenna. In such ascenario, the compatibility identifier 930 determine that the antennaport combination is incompatible for coincident use based on thedetection that the two ports do not share a physical antenna. In somecases, the compatibility identifier 930 may detect that the antenna portcombination includes antenna ports with independent transmit chains. Insuch cases, the compatibility identifier 930 may determine that theantenna port combination is compatible for coincident use based on thedetection of the independent transmit chains.

Compatibility signaling coordinator 935 may transmit a message (e.g., toa base station 105) indicating whether two or more antenna ports areavailable for coincident use based at least in part on the identifiedcompatibility of antenna port combinations. In some examples,compatibility signaling coordinator 935 may transmit an indication ofthe delay constraint determined by antenna port administrator 925 in themessage. In some cases, the message indicates a set of antenna portcombinations and a corresponding delay constraint for each. The delayconstraint may indicate a duration of time between using antenna portsin the corresponding antenna port combination. In some cases, themessage includes a compatible port set indicating an antenna portcombination that is compatible for concurrent use and thus that two ormore antenna ports are available for coincident use. In some cases, themessage includes an incompatible port set indicating an antenna portcombination that is incompatible for concurrent use. In some cases, themessage includes a compatible port set indicating a first set of antennaport combinations that are compatible for concurrent use and anincompatible port set indicating a second set of antenna portcombinations that are incompatible for concurrent use. In some cases,compatibility signaling coordinator 935 may convey the compatibility ofa set of antenna port combinations in a bit-map or matrix. In somecases, the message may include an indication of a number of antennaports available for coincident use—e.g., zero (meaning only one antennaport at a time), two, four, or six, or any other number—which may insome cases function as an indication of whether two or more of antennaports are available for coincident use.

Uplink/downlink manager 940 may communicate with a base station 105 viaone or more antenna ports. In some cases, the uplink/downlink manager940 may select an antenna port for communication based on compatibilitythe antenna port. In some cases, the uplink/downlink manager 940 mayreceive a scheduling message from the base station indicating an uplinkprecoder a combination of antenna ports. The uplink/downlink manager 940may apply the uplink precoder to the combination of antenna ports.

Hardware monitor 945 may determine a ratio of transmit chains tophysical antennas for an antenna port combination. In some cases, thecompatibility identifier 930 may identify compatibility of an antennaport combination based on the ratio. The hardware monitor 945 may detectthat a number of physical antennas associated with an antenna portcombination are co-located on an antenna panel. In such cases, thecompatibility identifier 930 may identify compatibility of an antennaport combination based on the detection. In some cases, the hardwaremonitor 945 may detect that the antenna ports in an antenna portcombination share a transmit chain. In such cases, the compatibilityidentifier 930 may determine that the antenna port combination isincompatible for coincident use based on the detection.

Transmitter 920 may transmit signals generated by other components ofthe device. In some examples, the transmitter 920 may be collocated witha receiver 910 in a transceiver module. For example, the transmitter 920may be an example of aspects of the transceiver 1035 described withreference to FIG. 10. The transmitter 920 may utilize a single physicalantenna or a set of physical antennas.

FIG. 10 shows a diagram of a system 1000 including a device 1005 thatsupports antenna port compatibility signaling in accordance with aspectsof the present disclosure. Device 1005 may be an example of or includethe components of wireless device 805, wireless device 905, or a UE 115as described above, e.g., with reference to FIGS. 8 and 9. Device 1005may include components for bi-directional voice and data communicationsincluding components for transmitting and receiving communications,including communications manager 1015, processor 1020, memory 1025,software 1030, transceiver 1035, antenna 1040, and I/O controller 1045.These components may be in electronic communication via one or morebuses (e.g., bus 1010). Device 1005 may communicate wirelessly with oneor more base stations 105 (e.g., using one or more antenna ports).

Processor 1020 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a central processing unit (CPU), amicrocontroller, an ASIC, an FPGA, a programmable logic device, adiscrete gate or transistor logic component, a discrete hardwarecomponent, or any combination thereof). In some cases, processor 1020may be configured to operate a memory array using a memory controller.In other cases, a memory controller may be integrated into processor1020. Processor 1020 may be configured to execute computer-readableinstructions stored in a memory to perform various functions (e.g.,functions or tasks supporting antenna port compatibility signaling).

Memory 1025 may include random access memory (RAM) and read only memory(ROM). The memory 1025 may store computer-readable, computer-executablesoftware 1030 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 1025 may contain, among other things, a basic input/outputsystem (BIOS) which may control basic hardware or software operationsuch as the interaction with peripheral components or devices.

Software 1030 may include code to implement aspects of the presentdisclosure, including code to support antenna port compatibilitysignaling. Software 1030 may be stored in a non-transitorycomputer-readable medium such as system memory or other memory. In somecases, the software 1030 may not be directly executable by the processorbut may cause a computer (e.g., when compiled and executed) to performfunctions described herein.

Transceiver 1035 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1035 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1035 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas. The transceiver 1035 mayfacilitate communications over antennas 1040, which may be examples ofthe physical antennas 315 described herein.

I/O controller 1045 may manage input and output signals for device 1005.I/O controller 1045 may also manage peripherals not integrated intodevice 1005. In some cases, I/O controller 1045 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 1045 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem. In other cases, I/O controller 1045 may represent or interactwith a modem, a keyboard, a mouse, a touchscreen, or a similar device.In some cases, I/O controller 1045 may be implemented as part of aprocessor. In some cases, a user may interact with device 1005 via I/Ocontroller 1045 or via hardware components controlled by I/O controller1045.

FIG. 11 shows a flowchart illustrating a method 1100 for antenna portcompatibility signaling in accordance with aspects of the presentdisclosure. The operations of method 1100 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1100 may be performed by a communications manager as describedwith reference to FIGS. 8 and 9. In some examples, a UE 115 may executea set of codes to control the functional elements of the device toperform the functions described below. Additionally or alternatively,the UE 115 may perform aspects of the functions described below usingspecial-purpose hardware.

At block 1105 the UE 115 may identify a plurality of antenna portsassociated with the UE 115 for communication with a base station. Theoperations of block 1105 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1105 may be performed by an antenna port administrator asdescribed with reference to FIG. 9.

At block 1110 the UE 115 may identify the compatibility of at least oneantenna port combination of the plurality of antenna ports forcoincident use by the UE 115. The operations of block 1110 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of block 1110 may be performed by acompatibility identifier as described with reference to FIG. 9.

At block 1115 the UE 115 may transmit a message to the base stationindicating whether two or more antenna ports are available forcoincident use based at least in part on the identified compatibility.The operations of block 1115 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1115 may be performed by a compatibility signaling coordinator asdescribed with reference to FIG. 9.

At block 1120 the UE 115 may communicate with the base station via atleast one of the plurality of antenna ports. The at least one of theplurality of antenna ports may be selected based at least in part on theidentified compatibility. The operations of block 1120 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1120 may be performed by a uplink/downlinkmanager as described with reference to FIG. 9.

FIG. 12 shows a flowchart illustrating a method 1200 for antenna portcompatibility signaling in accordance with aspects of the presentdisclosure. The operations of method 1200 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1200 may be performed by a communications manager as describedwith reference to FIGS. 8 and 9. In some examples, a UE 115 may executea set of codes to control the functional elements of the device toperform the functions described below. Additionally or alternatively,the UE 115 may perform aspects of the functions described below usingspecial-purpose hardware.

At block 1205 the UE 115 may identify a plurality of antenna portsassociated with the UE 115 for communication with a base station. Theoperations of block 1205 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1205 may be performed by an antenna port administrator asdescribed with reference to FIG. 9.

At block 1210 the UE 115 may identify a compatibility of at least oneantenna port combination of the plurality of antenna ports forcoincident use by the UE 115. The operations of block 1210 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of block 1210 may be performed by acompatibility identifier as described with reference to FIG. 9.

At block 1215 the UE 115 may determine a delay constraint between usingantenna ports in the at least one antenna port combination. Theoperations of block 1215 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1215 may be performed by an antenna port administrator asdescribed with reference to FIG. 9.

At block 1220 the UE 115 may transmit a message to the base stationindicating the compatibility and the delay constraint. The operations ofblock 1220 may be performed according to the methods described herein.In certain examples, aspects of the operations of block 1220 may beperformed by a compatibility signaling coordinator as described withreference to FIG. 9.

At block 1225 the UE 115 may communicate with the base station via atleast one of the plurality of antenna ports. The at least one of theplurality of antenna ports may be selected based at least in part on theindicated compatibility and delay constraint. The operations of block1225 may be performed according to the methods described herein. Incertain examples, aspects of the operations of block 1225 may beperformed by a uplink/downlink manager as described with reference toFIG. 9.

FIG. 13 shows a flowchart illustrating a method 1300 for antenna portcompatibility signaling in accordance with aspects of the presentdisclosure. The operations of method 1300 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1300 may be performed by a communications manager as describedwith reference to FIGS. 8 and 9. In some examples, a UE 115 may executea set of codes to control the functional elements of the device toperform the functions described below. Additionally or alternatively,the UE 115 may perform aspects of the functions described below usingspecial-purpose hardware.

At block 1305 the UE 115 may identify a plurality of antenna portsassociated with the UE 115 for communication with a base station. Theoperations of block 1305 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1305 may be performed by an antenna port administrator asdescribed with reference to FIG. 9.

At block 1310 the UE 115 may identify a compatibility of at least oneantenna port combination of the plurality of antenna ports forcoincident use by the UE. The operations of block 1310 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1310 may be performed by a compatibilityidentifier as described with reference to FIG. 9.

At block 1315 the UE 115 may transmit a message to the base stationindicating the compatibility. The operations of block 1315 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of block 1315 may be performed by acompatibility signaling coordinator as described with reference to FIG.9.

At block 1320 the UE 115 may receive a scheduling message from the basestation indicating an uplink precoder for the at least one of theplurality of antenna ports for communicating with the base station. Theoperations of block 1320 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1320 may be performed by a uplink/downlink manager as describedwith reference to FIG. 9.

At block 1325 the UE 115 may apply the uplink precoder to the at leastone of the plurality of antenna ports. The operations of block 1325 maybe performed according to the methods described herein. In certainexamples, aspects of the operations of block 1325 may be performed by auplink/downlink manager as described with reference to FIG. 9.

At block 1330 the UE 115 may communicate with the base station via atleast one of the plurality of antenna ports. The at least one of theplurality of antenna ports may be selected based at least in part on theindicated compatibility. The operations of block 1330 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1330 may be performed by a uplink/downlinkmanager as described with reference to FIG. 9.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releasesmay be commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE and LTE-A are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM aredescribed in documents from the organization named “3rd GenerationPartnership Project” (3GPP). CDMA2000 and UMB are described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). The techniques described herein may be used for the systems andradio technologies mentioned above as well as other systems and radiotechnologies. While aspects of an LTE or an NR system may be describedfor purposes of example, and LTE or NR terminology may be used in muchof the description, the techniques described herein are applicablebeyond LTE or NR applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A or NR network in which differenttypes of eNBs provide coverage for various geographical regions. Forexample, each eNB, next generation NodeB (gNB), or base station mayprovide communication coverage for a macro cell, a small cell, or othertypes of cell. The term “cell” may be used to describe a base station, acarrier or component carrier associated with a base station, or acoverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), gNB, Home NodeB, aHome eNodeB, or some other suitable terminology. The geographic coveragearea for a base station may be divided into sectors making up only aportion of the coverage area. The wireless communications system orsystems described herein may include base stations of different types(e.g., macro or small cell base stations). The UEs described herein maybe able to communicate with various types of base stations and networkequipment including macro eNBs, small cell eNBs, gNBs, relay basestations, and the like. There may be overlapping geographic coverageareas for different technologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers).

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein-including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, asused herein, the phrase “based on” shall not be construed as a referenceto a closed set of conditions. For example, an exemplary step that isdescribed as “based on condition A” may be based on both a condition Aand a condition B without departing from the scope of the presentdisclosure. In other words, as used herein, the phrase “based on” shallbe construed in the same manner as the phrase “based at least in parton.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media maycomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication at a userequipment (UE) having a plurality of antenna ports, comprising:identifying, among the plurality of antenna ports, a number of antennaports that are available for coincident use by the UE; transmitting to abase station, based at least in part on the identifying, an indicationof the number of antenna ports available for coincident use; andtransmitting, based at least in part on the indication, a set ofsounding reference signals (SRSs) within a same symbol period, whereineach SRS of the set of SRSs is transmitted via a respective antenna portof a set of antenna ports, and wherein the number of antenna portsavailable for coincident use is greater than or equal to a number ofantenna ports included in the set of antenna ports.
 2. The method ofclaim 1, wherein: identifying the number of antenna ports that areavailable for coincident use comprises identifying a number of SRSs thatthe UE is capable of transmitting in a same symbol period; and theindication of the number of antenna ports available for coincident useindicates the number of SRSs that the UE is capable of transmitting inthe same symbol period.
 3. The method of claim 2, wherein the number ofSRSs that the UE is capable of transmitting in the same symbol periodcomprises a number of precoded SRSs that the UE is capable oftransmitting in the same symbol period.
 4. The method of claim 1,wherein each SRS resource of the set of SRSs is transmitted via a pairof SRS antenna ports.
 5. The method of claim 1, further comprising:receiving a scheduling or sounding reference signal configurationmessage from the base station indicating an uplink precoder for at leastone of the plurality of antenna ports for communicating with the basestation; and applying the uplink precoder to the at least one of theplurality of antenna ports.
 6. The method of claim 1, furthercomprising: receiving a scheduling message from the base stationindicating at least one of the plurality of antenna ports; and receivinga downlink transmission over the at least one of the plurality ofantenna ports.
 7. An apparatus for wireless communication at a userequipment (UE) having a plurality of antenna ports, comprising: aprocessor; memory coupled to the processor; and instructions stored inthe memory and operable, when executed by the processor, to cause theapparatus to: identify, among the plurality of antenna ports, a numberof antenna ports that are available for coincident use by the UE;transmit to a base station, based at least in part on the identifying,an indication of the number of antenna ports available for coincidentuse; and transmit, based at least in part on the indication, a set ofsounding reference signals (SRSs) within a same symbol period, whereineach SRS of the set of SRSs is transmitted via a respective antenna portof a set of antenna ports, and wherein the number of antenna portsavailable for coincident use is greater than or equal to a number ofantenna ports included in the set of antenna ports.
 8. The apparatus ofclaim 7, wherein: the instructions operable to cause the apparatus toidentify the number of antenna ports that are available for coincidentuse comprise instructions operable to cause the apparatus to identify anumber of SRSs that the UE is capable of transmitting in a same symbolperiod; and the indication of the number of antenna ports available forcoincident use indicates the number of SRSs that the UE is capable oftransmitting in the same symbol period.
 9. The apparatus of claim 8,wherein the number of SRSs that the UE is capable of transmitting in thesame symbol period comprises a number of precoded SRSs that the UE iscapable of transmitting in the same symbol period.
 10. The apparatus ofclaim 8, wherein the instructions operable to cause the apparatus totransmit the set of SRSs comprise instructions operable to cause theapparatus to transmit each SRS resource of the set of SRSs via a pair ofSRS antenna ports.
 11. The apparatus of claim 7, wherein theinstructions are further operable to cause the apparatus to: receive ascheduling or sounding reference signal configuration message from thebase station indicating an uplink precoder for at least one of theplurality of antenna ports for communicating with the base station; andapply the uplink precoder to the at least one of the plurality ofantenna ports.
 12. The apparatus of claim 7, wherein the instructionsare further operable to cause the apparatus to: receive a schedulingmessage from the base station indicating at least one of the pluralityof antenna ports; and receive a downlink transmission over the at leastone of the plurality of antenna ports.
 13. An apparatus for wirelesscommunication at a user equipment (UE) having a plurality of antennaports, comprising: means for identifying, among the plurality of antennaports, a number of antenna ports that are available for coincident useby the UE; means for transmitting to a base station, based at least inpart on the identifying, an indication of the number of antenna portsavailable for coincident use; and means for transmitting, based at leastin part on the indication, a set of sounding reference signals (SRSs)within a same symbol period, wherein each SRS of the set of SRSs istransmitted via a respective antenna port of a set of antenna ports, andwherein the number of antenna ports available for coincident use isgreater than or equal to a number of antenna ports included in the setof antenna ports.
 14. The apparatus of claim 13, wherein: the means foridentifying the number of antenna ports that are available forcoincident use comprise means for identifying a number of SRSs that theUE is capable of transmitting in a same symbol period; and theindication of the number of antenna ports available for coincident useindicates the number of SRSs that the UE is capable of transmitting inthe same symbol period.
 15. The apparatus of claim 14, wherein thenumber of SRSs that the UE is capable of transmitting in the same symbolperiod comprises a number of precoded SRSs that the UE is capable oftransmitting in the same symbol period.
 16. The apparatus of claim 13,wherein the means for transmitting the set of SRSs comprise means fortransmitting each SRS resource of the set of SRSs via a pair of SRSantenna ports.
 17. The apparatus of claim 13, further comprising: meansfor receiving a scheduling or sounding reference signal configurationmessage from the base station indicating an uplink precoder for at leastone of the plurality of antenna ports for communicating with the basestation; and means for applying the uplink precoder to the at least oneof the plurality of antenna ports.
 18. The apparatus of claim 13,further comprising: means for receiving a scheduling message from thebase station indicating at least one of the plurality of antenna ports;and means for receiving a downlink transmission over the at least one ofthe plurality of antenna ports.
 19. A non-transitory computer readablemedium storing code for wireless communication at a user equipment (UE)having a plurality of antenna ports, the code comprising instructionsexecutable by a processor to: identify, among the plurality of antennaports, a number of antenna ports that are available for coincident useby the UE; transmit to a base station, based at least in part on theidentifying, an indication of the number of antenna ports available forcoincident use; and transmit, based at least in part on the indication,a set of sounding reference signals (SRSs) within a same symbol period,wherein each SRS of the set of SRSs is transmitted via a respectiveantenna port of a set of antenna ports, and wherein the number ofantenna ports available for coincident use is greater than or equal to anumber of antenna ports included in the set of antenna ports.
 20. Thecomputer readable medium of claim 19, wherein: the instructionsexecutable by the processor to identify the number of antenna ports thatare available for coincident use comprise instructions executable by theprocessor to identify a number of SRSs that the UE is capable oftransmitting in a same symbol period; and the indication of the numberof antenna ports available for coincident use indicates the number ofSRSs that the UE is capable of transmitting in the same symbol period.21. The computer readable medium of claim 20, wherein the number of SRSsthat the UE is capable of transmitting in the same symbol periodcomprises a number of precoded SRSs that the UE is capable oftransmitting in the same symbol period.